The present invention relates to a resist developing method by magnetic field controlling, a resist developing apparatus and a method of fabricating a semiconductor device.
For manufacturing a semiconductor device of the next generation, for example, 1-Gbit DRAM, it is aimed to use a ground rule of 0.15 .mu.m or less of a circuit pattern formed via resist coating, exposure, development and etching. For increasing the yield of semiconductor chips and improving the productivity, it is required that the pattern size is uniform in whole surface of a semiconductor wafer. Further, uniformity of the pattern size is required to be more excellent than that obtained by the present technique. Concretely, tolerance in error of a fabricated pattern size with respect to the designed size is more severely restricted to .+-.5%, which is .+-.10% in the present condition. To meet such requirements become more difficult with enlargement of the size of a semiconductor wafer from 8 inch to 12 inch.
For satisfying the above-described requirements, it is investigated to change KrF excimer laser having a wavelength of 248 nm used in a present exposure system to ArF excimer laser having a wavelength of 193 nm. However, the change of a light source requires improvement of the entire exposure system including a resist. Therefore, it is necessary to improve lithography process to satisfy the above-described requirement using the present exposure system.
In an advanced resist process, there is adopted a method in which a chemically amplified positive resist containing an acid generator is used and development is conducted using an alkaline developing solution, for example, an aqueous tetramethylammonium hydroxide (TMAH) solution. Concretely, a resist is applied to a semiconductor wafer and exposed to light by which an acid generates from an acid generator in the resist. By the action of the generated acid, a substituent having dissolution inhibiting ability, for example, a t-butyl ester group, is released from a resist resin and the resin becomes soluble in an alkali solution (a). On the other hand, TMAH in a developing solution is dissociated into N(CH.sub.3).sub.4.sup.+ ion and OH.sup.- ion (b). Then, development progresses by the neutralization reaction of a cation in the developing solution with the resist component which has become alkali-soluble. This reaction model is represented by the following formula. ##STR1##
The ions in the developing solution are transported by diffusion and convection and reach the reaction site of the resist to carry out development. However, by the reaction of an alkali in the developing solution with the alkali-soluble component in the resist, a neutral reaction products are produced, and these reaction products prevent another ions from reaching the reaction site of the resist. Therefore, depending on the position in the semiconductor wafer surface, there is a possibility that the above-described neutralization reaction does not progress sufficiently. As a result, uniformity of a resist pattern is lost in the semiconductor wafer surface.